Turbulence controlled steam iron



R. H. DuNcANsoN 2,793,448

May 28, 1957 TURBULENCE coNTRoLLEu STEAM IRON Filed Aug. 19, 1954 2shets-sneet 1 AJM/W A rroRNgr May 28, 1957 R. H. DuNcANsoN 2,793,448

TuaBuLENcEcoNTRoLLED STEAM IRON.

Filed Aug. 19, 1954 2 Sheets-Sheet 2 1 l INVENToR.-

Aoberz H Dal/)cansan JM/2mm Arroz/ver TURBULENCE coNTRoLLED STEAM inoRobert H. Duncaxison, Minneapolis, Minn., assigner to General Mills,Inc., a corporation of Delaware Application August 19, 1954, Serial No.450,875

Claims. (Cl. 158-77) This invention relates generally to steam irons ofthe domestic variety, and pertains more particularly to a steam ironhaving improved operating characteristics.

In the designing of steam irons there have been two extremes that havebeen most widely adopted. Probably the earlier of these `extremes hasbeen the tea kettle type where the entire quantity of water must beraised to boiling temperature before steam is made available for ironingpurposes. Not only does the user of such an iron have to wait arelatively long period of time for steam to be generated, but certainsafety problems must be overcome to assure that dangerous pressures arenever reached.

The other extreme, which has proved to be the more generally employed'type, is the so-called flash variety where the water is permitted toflow drop by drop from a supply reservoir into a region or chamber ofconcentrated heat, the water so fed being instantly converted intosteam. With this style of iron, however, difficulties have beenencountered as a result of attempts to steam iron before the propergenerating chamber temperature has been reached, and the waterintroduced flows onto the fabric with attendant spotting thereof in manyinstances. On the other hand, the steam generating temperature maybecome too hot with the consequence that the steam becomes superheatedto such an extent that the operation is not wholly satisfactory, forexperience has demonstrated that the pressing operation is moreefficient in many situations where the stream engages the fabric in arelatively moist condition.

Compromising the foregoing extremes is a design involving theutilization of a boiler having a relatively limited capacity, thelimited capacity permitting entrance to the boiler of only a smallVolume of water. By withdrawing the steam thus produced from the upperregion of the relatively small steam generating chamber or boiler, thatis above the water level in the boiler, water does not flow directly tothe ironing face of the soleplate when the boiler is below boilingtemperature. Also, one does not have to wait very long for steam to begenerated, inasmuch as the limited volume of water need be the onlywater to reach such a temperature. Thus, it will be recognized that thisintermediate design possesses considerable merit and promise, and it iswith this kind of steam iron that the present invention is primarilyconcerned.`

While the above alluded to intermediate type of iron does actuallyovercome the enumerated difficulties set forth above, it is not entirelydevoid of difficulties, the foremost of which stems from turbulence attimes within the limited or predetermined small volumetric capacity ofthe boiler chamber. As a result of excessive turbulence, it is possiblefor an objectionable amount of water in particle or globule form to becarried to the pressing face along with the steam. This water isundesirable in a number of instances, for while it is not a directstream, nonetheless it has the propensity to spot certain vvulnerablefabrics.

The solution of this turbulence problem has not been Patented May 28,1957 ICC an easy task. If water from the reservoir could be fed into thesteam generating chamber or well at a constant temperature and ataregulated ow equal to the rate at which steam is formed and escapes, theturbulence would be constant and could be more readily held in check bytransmitting less heat to the chamber where the conversion is takingplace. Such an ideal situation does not occur, and instead the operationis of a cyclic nature, there being a build up of turbulence, a period ofturbulence, a diminution of turbulence, a period of proper generationfollowed perhaps by a period of relative quiescence. Probably whathappens is that with a wide open valve, which permits entrance of Waterto the boiler from the reservoir, the water enters until pressuredevelops in the boiler area to such an extent that it is greater thanthe head of water in the reservoir. Obviously, with the iron v beingmoved back and forth `during a pressing operation even this head, due tothe jostling of water, will not be constant. However, now that no Water,or water at a reduced rate, is entering the boiler, the percolationwould be expected to increase. Soon the turbulence thus produced willsubside owing to the withdrawal of steam, and the boiler pressure ldropsto that of the reservoirs head. Such happenings are aggravated andcomplicated by the fact the iron itself is undergoing rapid temperaturechanges by reason of what transpires during the various ironing strokesand the pauses therebetween; if the iron is lifted momentarily from thefabric, heat conduction to the fabric is replaced by radiation to theatmosphere and vice versa.

Accordingly, it is believed manifest that uniform conditions do notprevail when using a steam iron and that operating characteristics couldstand to be improved upon in order to obtain a more idealistic steamiron. With this aim in View, it is an object of the instant invention tointroduce into the steam irons design what might be termed aself-compensating feature having an over-all effect of minimizingturbulence to such an extent that undesirable quantities of water willnot be ejected onto the fabric along with the extravasated steam. Morespecifically, it is within the purview of the invention to lead aportion of the steam and any entrained water over a course passing in aheat transfer relation with the boiler chamber. If the steam contains anobjectionable amount of water it will be cooler than if it carriedlittle or none, and the concomitant cooling action of such a mixed vaporwill have the immediate effect of withdrawing heat from the boiler withthe consequent result that the percolating severity will be lessened.Actually, relatively speaking, the above described happening is asuppressive one, for the percolation is constantly discouraged fromreaching excessive proportions by reason of the fact that once theturbulence begins to build up, the cooling effect progressivelyincreases, too. Hence for all intents and purposes the contemplatedconstruction is truly a selfcompensating one.

Another object of the invention is to devise a particular tank orreservoir structure that coacts in a unique fashion with the preferredconstruction utilized inthe realization of the above aim. In thisconnection, it is a desideratum of the invention to provide a compositereservoir formed of a casting and a resilient enveloping shell havingits lower edge telescoped thereover, the resilient character of theshell in conjunction with the casting permitting a sealing relationshipwith only a silicone cement in contradistinction to a brazed Vor weldedarrangement. While an economy is effected in assembling labor, it shouldbe pointed out that a further fabrication saving is brought about byvirtue of the casting serving as the bottom of the reservoir, it beingused anyway in the achievement of the earlier mentioned aim.

A further feature of the invention resides in the ernployment ofstructure in carrying out the foregoing objectives lending itselfreadily to the utilization of a breather system permitting the iron tobe rested on either of its sides. Y

Other objects will be in part obvious, and in part pointed out more indetail hereinafter.

The invention accordingly consists in the features of construction,combination of elements and arrangement of parts which will beexemplified in the construction hereafter set forth an-d the scope ofthe application which will be indicated in the appended claims.

Figure l is a longitudinal sectional View taken 1n the direction of line1-1 of Fig. 2;

Fig. 2 is a plan view of the boiler casting; A j h Fig. 3 is aperspective view taken in the general direction of line 3-3 of Fig. 2;

Fig. 4 is a fragmentary sectional View taken 1n the direction of line 44 of Fig. 2;

Fig. 5 is a plan view of the soleplate; and

Fig. 6 is a sectional view taken in the direction of line 6-6 of Figs. land 5.

To illustrate the invention, the drawings show a steamdry ironcomprising a soleplate 10 having a conventional encased heating element12 embedded therein. The soleplate is recessed at 14 for theaccommodation of a thermostatic switch structure designated generally bythe reference numeral 16, the switch structure including a bimetallicelement 18 and a pair of cooperable switch arms 20 and 22, each equippedwith a contact 24. In order to adjust the setting of the thermostaticswitch 16 there is provided an upstanding control shaft 26 having anadjusting knob 28 mounted at its upper end.

Describing the soleplate 10 in greater detail, it will be observed froman inspection of Figs. 5 and 6 that the heating element 12, whileactually embedded in the soleplate, is disposed within a pair of ribs 30and 32 integral with the main portion of this plate. These ribs areinstrumental in forming passages or grooves for the flow of steamtherethrough. However, more will be said later on concerning the preciseconstruction of these grooves and the particular pattern that theyfollow in guiding the steam to a plurality of outlet ports 34. Inasmuchas specific reference will be made hereinafter to certain of theseports, each has been rdistinguished one from the other by letter suixesa, b, c, d, e, and f.

Also formed integral with the soleplate 10 is a cavity 36 having aperipheral upstanding wall 38. As will be noted from Fig. 5 this cavityis somewhat triangular in configuration. Rearwardly disposed withreference to the cavity 36 which, as will later become more apparent,forms a part of the steam generating chamber or boiler is a pair ofpockets 40 and 42 which form part of the steam passage means leading tothe various ports or outlets 34. Forwardly located with respect to thecavity 36 is a pair of outwardly and rearwardly directed baffles 44 and46 and extending inwardly and forwardly are still further batles 48 and50.

Overlying the soleplate 10 is a cover plate 52, this cover plate havinga plurality of apertures 54, 56, 58 and 60 which will be referred towith greater particularity hereinafter. Superjacent the cover plate 52is a gasket member 62 provided with a pattern of apertures correspondingto those in the cover plate.

The purpose of the gasket 62 is to minimize the upward flow of heat fromthe soleplate 10 vi-a the cover plate 52 as well as to form a seal withrespect to a boiler casting designated in its entirety by the referencenumeral 64. This boiler casting 64 surmounts the soleplate 10 and isequipped with downwardly projecting posts or cleats 66, -any preferrednumber of which bear against the upper surface of the soleplate. For apurpose soon to be explained, the casting 64 has a downwardly turnedperipheral skirt or flange 68. Centrally disposed and integral with thecasting member 64 is an upstanding body portion 70 having 4at its loweredge a rather wide laterally extending ange '72 connecting with thedownwardly turned flange 68. Just to the front of the upstanding bodyportion 70 is an aperture 74 through which water is fed gravitationallyto the cavity 36 where steam conversion takes place. The upstanding bodyportion also contains a pair of vertically disposed passages 76 and 78leading upwardly from the cavity 36 and it will be appreciated that thepassages 76 and 78 are in registry with the apertures 56 and 58,respectively, located in the cover plate 52. In this way, unrestrictedupward flow of the steam generated in the cavity 36 is permitted. Atthis time perhaps it would be well to point out specifically that thecavity 36 in conjunction with the cover plate 52 forms a steamgenerating chamber or boiler having at its bottom a relatively smallpredetermined constant area which is a part of the top surface of thesoleplate 10. 5

Located in the upper region of the body portion '70 is a header chamber80 into which the vertical passages 76 and 78 lead, the bottom of thechamber 80 being of such contour that it drains in the direction of thepassages 76 and 78. Also, it should be pointed out that the chamber 80is of substantially larger volumetric capacity than that ofthe passages76 and '78, thereby producing a region of reduced steam velocity so thatthere is an attendant tendency for large drops of water to settle.Further, the header chamber 80 is formed with arcuate or cycloidalshaped ends 82 and 84, these ends forming rather sharp inwardlyextending projections 87 and 88. immediately forwardly and extendingsubstantially therebetween is a transverse bale 86 which is spaced inadvance of the projections suiciently so that the flow of steam mayprogress between said bafe 86 and the projections 87 and 88. Thefunction of the projections 87 and 88 is to provide a relatively sharpvertical edge against which unwantedparticles or globules of waterentrained in the steam will tend to cling so that they will not continueto flow along with the steam. Having passed between the baffle 86 andthe projections 87 and 88, the steam proceeds to a vertical passage 90which leads downwardly to a locus intermediate the pockets 4t) and 42.However, to either side of the forward portion of the entrance to thepassage 90 are inwardly directed projections 92 and 94, theseprojections providing additional sharp edges against which the undesiredparticles of water will tend to cling just as they do with reference tothe projections 87 and 88. Aiding in this action are oppositely issuingpockets 96 and 98 formed in part by said projections 92 and 94.

As has already been stated, the passage 90 leads downwardly to a locusintermediate the passages 40 and 42 and due to this intermedi'acy @theflow of steam passing downwardly divides so that substantially haflf ofthe supply proceeds toward one side of the iron and the other halftoward the opposite side of the iron. From the pockets 40 and 42 some ofthe steam is directed forwardly between the wall 38 surrounding thecavity 36 and the ribs 30 and 32, the steam as well passing over thatarea of the `top surface of the soleplate 10 lying between said ribs andthe wall 38. The significance of having at least a portion of the steampassing forwardly in the manner indicated resides in the fact that thepercolation of `the water within the cavity is apt to at times become sovigorous that Ithe resulting turbulence will cause excessively largeparticles or globules of water to pass upwardly via the passages 76 and78 andthis water when carried with the steam to the pressing face of theiron in many instances will cause objectionable spotting of fabricsvulnerable to excessive water. Stated otherwise, it is extremelydesirable in steam ironing to have any moisture in very fine particulateform rather than in large particles or globules. What happens is thatwhen the steam does contain an objectionable amount of water itt has amore pronounced cooling action against the walls of the passages throughwhich it is flowing. By causing at least a portion ofthe total output ofsteam from the cavity 36 to pass in heat transfer relationshiptherewith, then when the boiling action becomes so vigorous that theturbulence produces the aforementioned objectionable action, the actionis minimized or suppressed practically instantaneously with itsoccurrence. This stems from the fact as implied above thait the steamwith the objectionable amount of water withdraws heat from the cavity 36via the wall 38 and those portions of the top surface of the soleplatelying intermediate said wall tand the ribs 30 and 32. The cooling actionserves to reduce the turbulence and in this way isv self-compensating innature.

As stated above, in the exemplified embodiment only a portion of thesteam is :directed forwardly in a proximal relation with the cavity 36so as to influence the operating temperature thereof. This fraction ofsteam proceeds forwardly about the distal ends of the baffles 44 and 46,traversing a path over each of the ribs 30 and 32, then between thebaffles 44, 48 and 46, 50, respectively, and then outwardly through theparticular ports or outlets 34h, 34e, 34d, and 34e where it isextravasated onto the fabric being ironed. The remainder of the steam,that is the fraction which is not directly responsible for inuencing thetemperature of the cavity 36, is somewhat rearwardly directed over theribs 30 and 32 to the ports 34a and 34]". Quite obviously any particularnumber of ports 34 may be decided upon, mainly due to design factors:and to obtain an appropriate division of steam so that the requisiteamount of influence is obtained with respect to affecting thetemperature of the cavity 36.

In order to provide a reservoir for containing waiter to be fedgravitationally through the aperture 74 it is contemplated that iaresilient concave shell 100 be utilized, the lower edge of this shellbeing telescope'd over the downwardly projecting flange 68. Theparticular gauge of the sheet stock from which the shell is stamped andpressed should be adequate to pass a three foot drop test to a woodfloor, preferably in the neighborhood of 0.026 inch or possibly somewhatheavier. In this way, the iro-n will meet with both the AmericanStandard Association (A. S. A.) specification :and the NationalElectrical Manufacturing Association (N. E. M. A.) specificationapproved October 6, 1953. To provide an effective seal between theflange 68 and the shell 100 it is intended that a suitable siliconecement be employed and portions of this cement may be seen in Fig. 6,the portions there shown bearing the reference numerals` 102 :and 104.In this type of reservoir construction it will be appreciated thatfabrication costs are minimized inasmuch as the shell 100 does not haveto conform precisely to the more rigid flange 68 of the casting member64, for the cement itself will till up those small discrepancies in thefit that might remain, although the resiliency of the shell minimizessuch discrepancies. However, as observed in Fig. l the forward andrearward ends of the shell 100 have spacing such that these ends willlit snugly over the corresponding en'ds of the flange 68.

One nicety about the tank or reservoir construction described above liesin the fact that it cooperates with the upstanding body portion 70.Focusing attention on Fig. 6 for a moment, it will be seen that thesectional makeup of the body portion as shown illustrates that the topsurface thereof may be relatively planar. Because of this planar surfacethe shell 100 may also be substantially planar in this region and byutilizing a gasket 106 the under side of the top of the shell 100 may becaused to tact in a compressible manner :against the top surface of thebody portion 70. Since the casting member 64 is formed in effect withopen grooves such as the header chamber 80 and the side pockets 96 land98 as well as the interconnecting passageways, the top of the shell 160encloses these various passages so that there will be no avenue ofescape for the steam in this particular region other than via itsintended course.

In order to either open or close the Iaperture 74, it is planned that asuitable valve mechanism be employed and to achieve this aim theinvention has depicted a valve member 108 which seats within the upperend of the aperture 74. The valve member 108 is displaceably mountedwith reference to the aperture 74 by reason of a resilient springelement 110 substantially L-haped when viewed from one side as in Fig.l. The L-shaped spring element is ranchored intermediate its ends at 112by means of a screw 114 extending into the lateral flange 72 of thecasting member 64. The upper end 116 of the L-shaped spring serves as afollower for an internally fashioned cam 118 disposed in a downwardlyfacing recess 120 formed in a filler cap 122. The ller cap 122 ispressfitted within a grornrnet 124 which is anchored to the marginaledge 126 of an aperture provided in the top wall of the shell 100. By sorelating the parts, it will be apparent that rotation of the filler cap122 is instrumental in urging the end 116 of the spring 110 in such adirection that the valve member 108 will be moved into an open positionto permit water to ilow gravitationally from the reservoir i-nto thecavity .36 via the aperture 74. Of course, reverse rotation of the cap122 will release the opening force and by virtue of the inherentresiliency of the spring 110 the valve member 108 will close.

Although not important to :an understanding of the invention it will besta-ted in passing that in order to fill the reservoir formed by thecasting 64 and the shell 100 the f1ller cap 122 is raised somewhat sothat a side opening 123 is above the top surface of the shell 100.

Another feature of the invention resides in the provision of a breathersystem which has unique cooperation with the passages heretoforedescribed as well as the shell 100. For the purpose of understanding thefunctioning of the breather system now to be explained, particularreference should be had to Figs. 3 and 4. Referring first to Fig. 3, theupper end of the vertical passage adjacent its rear side has directcommunication with a relatively short rearwardly extending groove 130.This groove 130, which also appears in plan in Fig. 2, merges into arelatively deep transverse groove 132, the groove 132 extending towardeither side of the steam iron. At one Aend 134 ofthe groove 132 there isa reverse bend imparted thereto and the groove continues as indicated bythe number 136 toward the opposite side of the iron. Near the oppositeside of the iron there is a passage 138 angling downwardly.Communication is therefore established between the groove extension 136and the reservoir proper which, as hereinbefore stated, is formed by thecasting 64 and the shell-100. Specific reference to Fig. 4 should be hadin understanding the direction in which the passage 138 extends. The end140 of the groove 132 lying opposite the end 134 has a reverse bendimparted to it, also there being a short rearwardly extending portion142 which connects with an extended portion 144 leading toward theopposite side of the iron. The end of the groove extension 144 whichprovides direct communication with the reservoir proper has beenindicated by the reference numeral 146. Inasmuch as the various groovemeans 132, 136, 142, and 144 are covered by the top portion of the shell100, it will be appreciated that passages are in fact formed by theshell which serve to provide ingress or egress of air andvaporsbetween-the reservoir and-atmosphere, the path taken being by wayof the vertical passage 90 and the various passages over which the steamitself flows. Stated somewhat differently, the breathing action takesplace over a rather tortuous route between the reservoir proper and theatmosphere by way of the outlet ports 34. One point to be stressed inconnection with the breather system is that this breather systemfunctions irrespective of the particular side upon which the iron isrested for if the iron is placed with the passage 138 lowermost, thencommunication with the atmosphere Vis rendered possible by way of theend 146, the groove extension 144, the groove portion 142 and the groove132 which leads to atmosareas/is phere by way of the vertical passage 90as hereinbefore explained. If the iron is tilted into a side restposition with the end 146 lowermost, then of course communication isprovided through the passage 138 which connects with the grooveextension 136 and the groove 132 whi-ch has already been fully describedas connecting with the vertical passage 90. Thus the aforedescribedbreather system has special utility in steam irons which are to be siderested and in this respect it should be pointed out that the sideresting of steam irons is usually desirable inasmuch aslaboratory-conducted tests have demonstrated that less over-all ironingeffort is expended when side resting an iron in eontradistinction toupending an iron.

It is not believed necessary to present a detailed description of theoperation, for the operation is readily understandable from a study ofthe preceding material in conjunction with the drawings associatedtherewith. All that need be emphasized at this time is the fact that thesteam generated within the cavity 36, the wall 38 surrounding suchcavity in cooperation with the cover plate 52 as earlier explainedforming a boiler chamber, courses over a path that will permit at leasta portion of the total quantity of steam to flow in heat transferrelationship with the cavity 36. By so doing, with undesired turbulentconditions arising within the cavity 36, concomitantly producedexcessively moisture laden steam will extract heat from this region andthe heat withdrawn will have a cooling effect upon the boiler, whichcooling effect will cause the turbulent action to subside to the extentnecessary to reduce the emission of water globules with the steam.

The breather system per se is disclosed and claimed in application No.451,008, filed August 19, 1954, by Robert H. Duncanson and William G.Roll.

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the followingclaims is intended to cover all of the generic and specific features ofthe invention herein described and all statements of the scope of theinvention which, as a matter of language, might be said to falltherebetween.

I claim:

1. A steam iron comprising a soleplate having top and bottom surfaces,the top surface having a recess formed therein of a relatively smallpredetermined constant area, casting means surmounting the soleplateforming a steam generating boiler chamber with said recess, said castingmeans including a first substantially vertical passage leading upwardlyfrom said boiler chamber, a second substantially vertical passageleading downwardly to a locus on the top vsurface of said soleplatespaced laterally from said recess and groove means in the upper surfaceof said casting means communicating with said first and second passages,passage means leading from said locus having a portion thereof in heattransfer relationship with said boiler, and a relatively thin concaveshell member enveloping the upper portion of said casting means havingits lower edge telescoped over the lower portion of said casting meansto form a reservoir.

2. A steam iron comprising a soleplate having top and bottom surfaces,the top surface having a recess formed therein of a relatively smallpredetermined constant area providing a steam generating boiler chamber,casting means surmounting the soleplate including a body portion and aperipheral flange portion extending laterally from the base of said bodyportion, said body portion having a first substantially vertical passageleading upwardly from said recess, a second substantially verticalpassage leading downwardly to a locus on the top surface of saidsoleplate spaced laterally from said recess and groove means in theupper surface of said vbody portion communicating with said rst andsecond passages, passage means leading from said locus to the bottomsurface of said soleplate having a portion thereof in heat transferrelationship with said boiler, and a relatively thin concave shellmember engaging and covering the upper part of said body portion havingits lower edge telescoped over said peripheral flange portion to form areservoir defined by said body portion, flange portion and shell member,said body portion further including a passage communicating between saidreservoir and said boiler chamber to permit flow of liquid to saidboiler.

3. A steam iron comprising a soleplate having top and bottom surfaces,the top surface having a recess formed therein of a relatively smallpredetermined constant area providing a steam generating boiler chamber,casting means surmounting the soleplate including a body portion and aperipheral fiange portion extending laterally from the base of said bodyportion, said body portion having a first substantially vertical passageleading upwardly from said recess, a second substantially verticalpassage leading downwardly to a locus on the top surface of saidsoleplate spaced laterally from said recess and groove means in theupper surface of said body portion communicating with said first andsecond passages, passage means leading from said locus to the bottomsurface of said soleplate having a portion thereof in heat transferrelationship with said boiler, a relatively thin concave shell memberengaging and covering the upper part of said body portion having itslower edge telescoped over said peripheral flange portion to form areservoir defined by said body portion, ange portion and shell member,said body portion further including a passage communicating between saidreservoir and said boiler chamber to permit fiow of liquid to saidboiler, and additional groove means in the upper surface of said bodyportion connecting with the first mentioned groove means, saidadditional groove means having individual sections thereof extendingfirst to opposite sides of said body portion and then reversely todifferent opposite sides, said shell member also covering saidadditional groove means.

4. A steam iron comprising a soleplate having top and bottom surfaces, aboiler of limited volume having its lower end associated with saidsoleplate, means for heating said boiler chamber, substantially verticalpassage means leading upwardly from said boiler, second substantiallyvertical passage means displaced laterally from said boiler, thirdpassage means providing communication between the upper ends of saidfirst and second passage means including a header chamber substantiallylarger in volumetric capacity than that of said first passage means, andfourth passage means leading from the lower end of said second passagemeans having a portion thereof in heat transfer relationship with saidboiler.

5. A steam iron in accordance with claim 4 in which said header chambercontains a transverse bafiie and a bottom contoured so that drainage mayoccur in the direction of said first passage means.

References Cited in the file of this patent UNITED STATES PATENTS2,078,061 Cooper Apr. 20, 1937 2,316,907 Wallace Apr. 20, 1943 2,483,580Green et al. Oct. 4, 1949 2,499,184 Finlayson Feb. 28, 1950 2,506,941Scott May 9, 1950 2,557,732 Finlayson June 19, 1951 2,690,623 JepsonOct. 5, 1954

